Typical rubber hoses, for example, made of a blend of acrylonitrile-butadiene rubber and polyvinyl chloride (NBR/PVC blend) which is excellent in resistance to gasoline permeability, have been used for conveying fuel (fuel such as gasoline for engine) for automobiles or the like in view of their high vibration-absorbability, easy assembling or the like. However, for the purpose of global environment protection, the regulations have been recently tighten against permeation of fuel for automobiles or the like, and are anticipated to be further tighten in the future. Therefore, such hoses for conveying fuel are required further permeation resistance to fuel.
And, hoses for conveying fuel such as hydrogen gas used in fuel cells, or for conveying carbon dioxide gas refrigerant are required extremely high permeation resistance to such conveyed fluid as hydrogen gas, carbon dioxide gas.
However, with regard to this requirement hoses configured by organic materials only such as rubber or resin are difficult to satisfy such required resistance.
Under the circumstances, it is considered to form preferably a composite hose by combining with a corrugated metal tube as a barrier layer against permeation of conveyed fluid.
For example, U.S. Pat. No. 6,354,332 discloses a composite hose with a corrugated metal tube of this type.
Meanwhile, a corrugated shape or a performance based on the shape provides a corrugated metal tube with an effect of flexibility. A material of the corrugated metal tube itself is metal and does not have elasticity different from rubber or the like.
So, a hose combined with a such corrugated metal tube involves a problem that during conveying fluid, an internal pressure is repeatedly exerted to the corrugated metal tube, the corrugated metal tube is deformed repeatedly in a radially expanding and contracting manner, and then a stress, which acts on the corrugated metal tube, brings a result that the corrugated metal tube is readily fatigue-broken at an early stage.
Specifically, when the corrugated metal tube expands radially, a maximum or large pulling stress or the largest pulling stress acts on corrugation hills. And, when it is repeated, the corrugation hills are readily cracked in a circumferentially direction.
On the other hand, corrugation valleys are distorted and deformed while the corrugated metal tube expands and contracts radially. And, due to repeated distortion and deformation, the corrugation valleys are also readily cracked in a circumferentially direction.
In the composite hose with a corrugated metal tube of this type which have been proposed traditionally, an elastic material such as rubber fills in valley gaps between corrugation hills on an outer peripheral side of the corrugated metal tube. The elastic material penetrating in the valley gaps as a result serve to restrain above deformation of the corrugation hills and the corrugation valleys of the corrugated metal tube.
However, in case of a conventional composite hose with a corrugated metal tube, the above-mentioned elastic material penetrating in the valley gaps are provided without an intention of restraining excessive deformation of the corrugation hills and valleys of a corrugated portion.
Then, the inventors of the present invention manufactured a sample of a composite hose with a corrugated metal tube where an elastic filler is provided in valley gaps between corrugation hills on an outer peripheral side of the corrugated metal tube with an intention of restraining excessive deformation of the corrugated metal tube, specifically, of corrugation hills and valleys thereof, and evaluate the sample.
FIGS. 6(A), 6(B-1) and 6(B-2) show one sample as comparison example.
With reference to FIG. 6(A), reference numeral 200 indicates a corrugated metal tube of an inner layer of a composite hose 202 as a barrier layer against fluid permeation. Reference numeral 204 indicates an inner rubber layer, reference numeral 206 indicates a reinforcing layer formed by winding a reinforcing wire member, and reference numeral 208 indicates an outer rubber layer. Here, in the reinforcing layer 206, a winding density of the reinforcing wire member such as a reinforcing thread is 80% or less.
A part of the inner rubber layer 204 serves as an elastic filler 204A. As shown in FIG. 6(B-1), the elastic filler 204A penetrates in valley gaps 214 between corrugation hills 210, 210 of a corrugated portion on an outer peripheral side of the corrugated metal tube 200.
Reference numeral 212 indicates corrugation valleys of the corrugated portion.
The elastic filler 204A penetrating in the valley gaps 214 in such a manner serves to restrain excessive deformation of the corrugation hills 210 and the corrugation valleys 212, and this may restrain early fatigue fracture of the corrugated metal tube 200 resulting from a large pulling stress acting to the corrugation hills 210 and distortional deformation of the corrugation valleys 212.
However, in the composite hose with a corrugated metal tube shown in FIG. 6(A-1), although the elastic filler 204A is filled in the valley gaps 214 between the corrugation hills 210, 210, the corrugated metal tube 200 is not sufficiently durable and, as a result, the composite hose is not satisfactory in view of durable life.
Then, the inventors examined the cause of its insufficient durable life. It is found by the inventors that the elastic filler 204A penetrating in the valley gaps 214 escapes the valley gaps 214 radially outwardly under an internal pressure or the like which is exerted to the corrugated metal tube 200, as shown in FIG. 6(B-2), resulting that restraining force against deformation of the corrugation hills 210 and valleys 212 is diminished, the corrugation hills 210 and valleys 212 are largely deformed and it leads to fatigue fracture of the corrugated metal tube 200.
The present invention is made under the foregoing circumstances. It is an object of the present invention to provide a composite hose with a corrugated metal tube having a favorable durable life. In the present invention, the composite hose with a corrugated metal tube is constructed not to allow escape of the elastic filler filled in valley gaps between corrugation hills on outer peripheral side of the corrugated metal tube out of the valley gaps. Thus constructed composite hose is prevented from decrease in durable life.